Hydrolysis of manganese carbides Mn5C2 and Mn23C6

Abstract

Diffractographically pure manganese carbides Mn5C2 and Mn23C6 were hydrolyzed with water at 25 and 60 °C. Based on the model of contracting spherical particles in the carbide powder particulate system, the corrosion rates were calculated from the course of gas evolution during the hydrolysis; the values obtained were as follows in μm/h: Mn5C2: 1.2 ± 0.4 at 25 °C and 10 ± 3 at 60 °C, and Mn23C6: 0.15 ± 0.01 at 25 °C and 2.2 ± 0.2 at 60 °C. The hydrolysis gives rise to hydrogen and a concentration-decreasing sequence of predominantly saturated hydrocarbons, the fraction of C2 and higher hydrocarbons being about 6 times lower for Mn23C6 than for Mn5C2. The hydrogen and hydrocarbon contents of the mixture after hydrolysis are consistent with the assumed reaction course, where the adsorbed active hydrogen, formed during the hydrolysis reaction due to the metallic nature of the carbide, partly reacts with the methane arising from the hydrolysis of the C1 groups in the carbide and partly combines to molecular hydrogen.